calculate the resistance of 100 m long copper wire of radius 0.5 mm.resistivity of the copper is 1.72 x 10-8 ohmm
we know that the resistance is given as
R = ρL/A
here,
ρ = 1.72 x 10-8 ohm.m
L = 100 m
A = πr2 = π(0.5x10-3)2 = 7.85 x 10-7 m2
so,
R = ( 1.72 x 10-8 x 100 ) / 7.85 x 10-7
thus, resistance of the wire will be
R = 2.19 ohm